Fate Grand Order - Prison Tower Event Guide: 3rd Gate – Monster of R’yleh

Guide to the 3rd Gate during the FGO Prison Tower Event. Especially since this particular quest can be a pain to deal with, we've created an FGO event guide that will help you bring down that pesky boss at the 3rd Gate - Monster of R'yleh.

Prison Tower Event Guide: 3rd Gate – Monster of R’yleh

After defeating the lord at the second gate, the 3rd Gate now opens with Edmond Dantes leading the protagonist through the dungeon halls. Edmond Dantes tells the protagonist that he/she could just lay around if he/she wanted. However, as they approach the third gate, they discover that Gilles De Rais serves as the Avatar of Sloth as he had fallen far from his vows of knighthood.

Battle Video


AP Cost 20 Bond Point 615
EXP 15690 QP 6400
Tendency Berserker/Caster/Rider/Assassin First Reward Summoning Ticket x 1


Enemy Information
Battle 1/3
(Lvl 45/ Berserker/ 9771 HP)
(Lvl 45/ Berserker/ 9771 HP)
Iron Golem
(Lvl 42/ Berserker/ 11997 HP)
Battle 2/3
Crystal Golem
(Lvl 60/ Berserker/ 124,545 HP)
Battle 3/3
(Lvl 37/ Assassin/ 78,586 HP)
Gilles De Rais
(Lvl 92/ Caster/ 203,728 HP)
(Lvl 37/ Assassin/ 78,586 HP)


Drop Item Information
Ascension Skill Reinforce
Caster Monument
Ascension &
Skill Reinforce
Octuplet Crystal x3, Heart of the Foreign God x2


  • You’ll need a combination of servants that inflict damage almost immediately. My suggestion is to arm Elisabeth Bathory (Halloween) with Halloween Princess and quickly charge her up for the next round. While doing so, get two other servants that can inflict a defense debuff to deal heavy damage while arming at least one of them with an MLBed Purely Bloom CE.
  • Bringing a Rider class servant will definitely be useful. Especially a support servant like Saint Martha who has heals to continuously keep healing your Berserker. You can also bring Francis Drake for a quick spray-and-pray by buffing up the damage of the noble phantasm.
  • Ideally, your team would be Elisabeth Bathory (Halloween)Saint Martha, and Heracles. However, your team can vary so long as it can support each other.
  • Edmond Dantes doesn’t have much use here considering that there’s no Ruler class enemy that needs kicking.

FGO Prison Tower

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